In order for you to play Crusader Kings III on Linux with minimal graphics settings, your computer must meet the following requirements
Operating System:
Ubuntu 20.04 LTS
Processor (CPU):
Intel Core i5-750 | AMD FX 4300
Memory (RAM):
8 GB RAM
Graphics Card:
NVIDIA GeForce GTX 660 | AMD Radeon HD 7870 | Intel Arc A310 | Intel Iris Plus G7 | AMD Radeon Vega 11
Storage:
20 GB available space
In order to play Crusader Kings III on Linux with maximum graphics settings, you need a computer with a configuration no worse than the following
Operating System:
Ubuntu 20.04 LTS
Processor (CPU):
Intel Core i5-8400 | AMD Ryzen 5 1600X
Memory (RAM):
16 GB RAM
Graphics Card:
NVIDIA GeForce GTX 970 | AMD Radeon RX 480 | Intel Arc A580
Storage:
20 GB available space